Male ornamental coloration improves courtship success in a jumping spider, but only in the sun

In many animals, males display colorful ornaments to females during courtship, the effectiveness of which depends on the ambient lighting environment. While a variety of hypotheses exist to explain both presence of and variation in such traits, many propose that they function as signals and that their presence is required for or improves successful mating. In Habronattus pyrrithrix jumping spiders, males display brilliant, condition-dependent red faces and green legs to drab gray/brown females during courtship. We designed 2 experiments to first test if coloration is required for successful mating and then whether the role of color changes under varying light conditions. In Experiment 1, we paired individual males with virgin females under laboratory lighting and found that blocking either their red or green coloration, or both, had no effect on success (likelihood of copulation, copulation duration, latency to copulation, female aggression, or cannibalism) when compared with sham-treated males. In Experiment 2, we gave virgin females the choice between 2 simultaneously courting males, one with his red coloration blocked and the other that received a sham treatment, and ran trials outdoors in both the sun and the shade. Blocking red facial coloration reduced a male's ability to approach a female, but only when courting in the sun. These results suggest that ornamental coloration is not required for mating in H. pyrrithrix, but that red coloration improves success in certain contexts. We discuss implications for the evolution of elaborate, multimodal courtship displays by animals that interact in variable environments.